Cell Lab: Microscopy and Staining

Materials (per group)

1.1 Microscope

2.1- 2 toothpicks

3.pond water (part A)

4.1-2 drops Methylene blue stain (or other stain) (part B)

5.Elodea leaf.

6.optional idea: look at a culture of yeast (time permitting)

Part A:

1. Observe samples of pond water under various magnifications.

2. What do you see? Sketch what you observe. Make your drawings to scale.

Scanning
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Questions

1. Are there any single-celled organisms? Describe them.

2. Are there multicellular organisms? Describe them.

Part B: Cell staining.

No Stain:

  1. Make a wet mount of your cheek cells (see steps 2-7 below)
  2. Observe the cells without stain under the microscope.

With Stain:

1. Put a drop of methylene blue or other staining solution on a slide. Caution: methylene blue and other staining solutions will stain clothes and skin.

2. Gently scrape the inside of your cheek with the flat side of a toothpick. Scrape lightly.

3. Stir the end of the toothpick in the stain and throw the toothpick away.

4. Place a cover slip onto the slide

**(Note: An alternate staining procedure is to place a drop of stain next to the cover slip and then place a paper towel on the other side of the cover slip. This creates a wicking action that pulls the stain in)

5. Use the SCANNING objective to focus. You probably will not see the cells at this power.

6. Switch to low power. Cells should be visible, but they will be small and look like nearly clear purplish blobs. If you are looking at something dark dark purple, it is probably not a cell

7. Once you think you have located a cell, switch to high power and refocus. (Remember, do NOT use the coarse adjustment knob at this point)

---Sketch the cell at low and high power. Label the nucleus, cytoplasm, and cell membrane.

Draw your cells to scale.

Scanning
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Questions

1. What parts of the cell were visible without the stain? What parts were visible with the stain?

2. List 2 organelles that were NOT visible but should have been in the cheek cell.

3. Is the cheek cell a eukaryote or prokaryote? How do you know?

Part C: Elodea

  1. Observe a small piece of Elodea at low, medium and high power.
  2. Draw your cells to scale and label the parts that are visible.

Questions

1. Describe the similarities visible between plant and animal cells. What are the differences?

ALTERNATIVE: (Use Skin cells from your wrist instead)

Procedure:
1. Wash the underside of a wrist that will be sampled for epidermal cells with soap and water.
2. Stick a clean piece of clear tape on the underside of the washed wrist.
3. Gently remove the piece of tape from the wrist being careful to avoid getting fingerprints on the tape. A forceps might help to remove the tape and avoid fingerprinting the tape.
4. Place the tape, sticky-side up, on a clean microscope slide.
5. Stain the top, sticky side of the tape with 2 or 3 drops of 1% methylene blue solution.
6. Use a dissecting needle to gently place a cover slip over the sticky tape. Lower the cover slip down onto the tape and then remove the dissecting needle. This should help prevent staining your fingers. Caution: Use methylene blue carefully. It will stain most items including skin, clothing, and table tops.
7. Examine the slide under a microscope. Look for cells with low power first, and then switch to high power for details.